Portable electronic devices, such as mobile terminals, increasingly provide a variety of communications, multimedia, and/or data processing capabilities. For example, mobile terminals, such as cellphones and personal digital assistants, may provide access to data in a wide variety of multimedia formats, including text, pictures, music, and/or video.
Conventional mobile terminals often include a Global Positioning System (GPS) receiver that can be used to determine an approximate geographical location of the mobile terminal. In a typical GPS application, the GPS receiver collects and analyzes ranging measurements from signals transmitted by GPS satellites having known locations. More specifically, a constellation of satellites orbiting the earth continually emit a GPS radio signal. A GPS receiver, e.g., a hand-held radio receiver with a GPS processor, receives the radio signals from the closest satellites and measures the time that the radio signal takes to travel from the GPS satellites to the GPS receiver antenna. By multiplying the travel time by the speed of light, the GPS receiver can calculate a range for each satellite in view. Ephemeris information provided in the satellite radio signal typically describes the satellite's orbit and velocity, thereby generally enabling the GPS processor to calculate the position of the GPS receiver through a process of triangulation.
For example, the Garmin Forerunner® is a personal training device that includes a GPS receiver. The GPS receiver may accurately measure athletic performance data including distance, speed, time, altitude, pace, and/or other data that can be important to athletes in training for races. For instance, the Forerunner® can record a user's athletic performance data during a workout and playback the data during a later workout, allowing the user to compete against prior workouts. The Forerunner® also includes wireless heart rate monitor, so that a user can compare his/her pace and heart rate to a past performance over the same run. In addition, the Forerunner® allows a user enter a desired distance, time, and/or pace/speed for a workout, and displays a “Virtual Partner” that runs at the desired pace compared to the user's current pace. Accordingly, conventional mobile terminals including a GPS receiver can be used to accurately track a user's performance during an athletic event.